Gsxr1100M Charging Issues

[Nick.]

Hi there,

My 1100 slingshot appears not to be charging correctly. Basically, if I ride it with the lights on for a prolonged period (20 mins +), when I come to start it again, the battery doesn't have enough juice to turn the engine over, necessitating a bump start.

However, if ridden with no lights for a prolonged period, it turns over and starts fine. Now, I have tested it with the multimeter at the battery terminals and it shows:

Whilst running at 5k with no lights - 14.6v - 15.5v (seems to jump about)

Whilst running at 5k with lights - 14.6v ish, but dwindling

The battery has been tested in another slingshot and holds its charge when used in this bike with the lights on, so I suspect the regulator/rectifier is donald ducked. They appear to be buried in the alternator on these bikes and are £££, so I reckon it'd be easier to chuck another alternator in from a breakers...

Or am I barking up the wrong tree here with my diagnosis?

Thanks guys.

[lorenzo]

Can you get into the alternator somehow to see what's what, get some leads across the individual phases etc? 15.5ish and jumping about doesn't sound too healthy, you really want is 14.5ish and flat as you rev it up.